Arrangement for generating audible frequencies in high-frequency signaling



Nov. 23 31920. 1,608,003 7 W. SC HAFFER ARRANGEMENT FOR GENERATING AUDIBLE FREQUENCIES IN HIGH FREQUENCY SIGNALING Filed June 5, 1924 T LO A OSCILLA OR MENTOR WALTER SCHAFFER ATTORNEY fit ' signal.

Patented Nov. 23, 1926 UNITED STATES 1,608,003 PATENT oFFics.

WALTER scnArrnn, or BERLIN, GERMANY, Assrenon T e-nsnnnscnarr nnanrnosn TELEGRAPHIE M. B. H., or BERLIN, GERMANY, A CORPORATION or GERMANY.

ARRANGEMENT FOR GENERATING AUDIBLE FREQUENCIES IN HIGH-FREQUENCY SIGNALING. i

Application filed. June '5, 1924, $eria1 No.

My invention relates to an arrangement for generating audible frequencies for modulating a carrier Wave in signaling systems.

It has for its object to provide such an arrangement which will produce an audible frequency by means of two circuits, one of which contains a microphone and the other a telephone, the circuits being electrically coupled and the microphone and telephone being acoustically coupled.

Another object of the invention is to provide a similar arrangement employing an additional heterodyning circuit which can be usedto changethe frequency of the audible Other objects will be apparent to those skilled in the art from the following description and claims when considered. with the accompanying drawing, in which the single figure represents a circuit embodying 'my invention. I

There are already transmitting arrangements for wireless telegraphy which use radiofrequency vacuum tube transmitters, on the grid circuits of which are superimposed alternating currents of audible frequency. The generators of audible frequency have been, till now, buzzers, vacuum tubes oscillating in an audible frequency, commutators of direct current dynamos, the said com mutators consisting of a great number of segments, and various other devices.

All these known arrangements require a greater or smaller quantity of energy, for the generation of audible frequency and furthermore complicated and expensive auxiliary apparatus.

The present invention relates to a transmitter of audible frequency, which is generatedin a very simple manner. The invention uses for this purpose the known acoustic phenomenon which occurs if a circuit containing a telephone is suitably coupled to a microphone circuit and the microphone is acoustically coupled to a telephone. Under these conditions an intensive musical note is generated, the frequency of which depends on the natural vibration of the telephone.

The drawing shows an application of this invention'which may be employed for any telephone connection using separately excited or self-excited transmitting vacuum tubes. A is the aerial and iscoupled to the 717,932, and in Germany .lune' 27, 1923.

oscillator tube It. The aerial circuit is grounded through C01l'9 for a purpose explained hereinafter.

The output circuit of the tubes B oomprises condenser 1, coil 2 and condenser The input circuit is connected across condenser 3. The plate current of tube R is supplied by means of B battery 4L through coil 5 and thermionic'tube R which tube operates as a variable resistance in the plate circuit of tube R, the resistance of tube R being controlled by the potential on its grid. Connected to the input circuit of thetube it is coil 6. Coupled to coil 6 is coil which is in circuit with microphone M, battery 8, and key S, comprising the microphone circuit. 7

Acoustically coupled'to microphone M is telephone T. Telephone T is in an aperiodic telephone circuit, which is coupled to coil 9 in the antenna circuit by means of coil 7. In this circuit is also a. rectifier K. Connectedacross telephone T is condenser The acoustioand electrical coupling of the telephone and microphone circuits gives rise to a sustained audible oscillation, the frequency of which is determined by the acoustic properties and arrangement of the microphone hi and telephone T. Key S is operated according to the signal it is desired to transmit which may be in the form of the usual Morse characters.

' It will be easily understood that when the key S is operated anv audible frequency is generated which is impressed upon the grid circuit of tube R and va 'ies the resistance in the plate circuit of tube R thereby Varying the amplitude of the carrier wave generated by the oscillating tube R in accordance with the signal which is being sent. i

It will be easily understood that the a'udible oscillations are generated, when key S is closed by the regenerative effect of the modulated carrier wave being fed back into the telephone circuit by means f coupling coils 7 and 9. The modulated carrier wave, after being rectified by rectifier K is impressed on telephone T in phase with the audible oscillations which are being generated by telephone T, and reenforces'them.

If it is desired to vary the audible frequency this can be done by means of a heterodyne circuit U connected in parallel to the telephone T. The oscillations of the heterodyning circuit Will then be combined With the sustained oscillations of the microphone-telephone circuits to produce the new and desired audible frequency.

It Will easily be understood by those skilled in the art that the sending key S may be in the telephone circuit instead of in the microphone circuit Having described a single embodiment of my invention, 1 am entitled to all modifications thereof as fairly come Within the scope of the following claims.

Having described my invention, What I claim is:

1. An arrangement for transmitting signals by means of a carrier Wave, comprising a transmitting circuit, a source of carrier waves coupled thereto, a first circuit containing a first electro-acoustic device, a second circuit containing a second electroacoustic crevice, said first and second electrovacoustic devices being acoustically coupled,

means for coupling said first and second circuits to obtain sustained oscillations, and means for modulating the carrier Wave with said sustained oscillations.

2. An arrangement for transmitting signals by means of a carrier Wave, comprising a transmitting circuit, a source of carrier Waves coupled thereto, a first circuit containing a microphone, a second circuit containing a telephone and rectifier, said second circuit being coupled to said transmitting circuit, said microphone being acoustically coupled to said telephone and means for modulating the carrier Wave by oscillations generated in said first circuit.

3. An arrangement for transmitting signals by means of a carrier Wave, comprising a transmitting circuit, a source of carrier Waves coupled thereto, a first circuit containing a first electro-acoustic device, a second circuit containing a second electroacoustic device, said first and second elect-roacoustic devices being acoustically coupled, means for coupling said first and second circuits to obtain sustained oscillations, heterodyne means coupled to one of said first and second circuits for producing a beat With said sustained oscillations, and means for modulating the carrier Wave With said beat. 4. in combination, a transmitting key associated with audio frequency responsive means, means for transmitting a carrier wave, means for modulating the transmitting means by the audio frequency and means for reacting on the audio frequency means from ei'iects produced by, the audio means on the modulating means to accentuate the audio frcquency- 5. In combination, a transmit-ting key associated with audio frequency esponsive means, means for transmitting a carrier Wave, means for modulating thetransmitting means by the audio frequency and means for reacting on the audio fr quency means from effects produced by the audio means on the modulating means to accentuate the audio frequency, whereby the tra smittingkey causes the audio means to become operative and inoperative alternately according to the signal desired to be mitted.

'6. In combination,means for transmit ting a carrier Wave, audio frequency mes means for modulating the transmitting means by the audio frequency means and for reacting on the audio frequency means from eiiects produced by the audio means on the modulating means to ace ntuate the audio frequency.

7. In, combination, means for transmitting a carrier Wave, audio frequency means, means for modulating the transmitting means by the audio frequency means and means for reacting on the audio frequency means from efieots produced by the audio means on the modulating means to accentuate the audio frequency, and means for pro ducing a beat note with the audio frequenc 8. 'ln combination,means for transmi ting a carrier Wave, secondary frequency means, means for modulating the transmit ting means by the secondary frequency means and means for reacting on the second ary frequency means from effects produced by the secondary means on the inoculating means to accentuate the secondary frequency, means for combining with the secondary frequency means, oscillations generated by a heterod'yning circuit, whereby the natural oscillations of the secondary frequency conibines with the heterodyne set of oscillations to produce a beat note thereby attaining a larger note-scale.

' WALTER SCHAFFER.

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